The objective of this study is to determine the molecular mechanisms associated with eccentric exercise-induced insulin resistance. In particular, we will look at the effects of a single bout of unaccustomed eccentric exercise on insulin stimulation of insulin receptor substrate (IRS)-1 and IRS-2 mediated PI3-kinase activation and mitogen activated protein kinase (MAPK) tryosine phosphorylation. The activation of these enzymes has been shown to be critical in the regulation of glucose uptake and glycogen synthase activation (5). In addition, immunohistochemical levels of tumor necrosis factor-alpha (TNF-a), a regulator of inflammation, will be examined to determine the extent to which the immune response associated with eccentric exercise-induced muscle damage is responsible for the transient insulin resistance.